I have reinstalled OE several times and verified that OE is the default email program, both in OE and in Windows control panel.
Nothing I have tried has ever corrected the issue with "mailto" not functioning. I finally gave up on using that feature but here
is a screenshot of my settings FYI. I see that I am not the only one experiencing this issue. It's not a major problem, I just
work around it by copying and pasting the email address into OE when needed.